Shockproof electromagnet



APrll 30, 1946- 'r. M. SPITLER SHOCKPROOF ELECTROMAGNET Filed Aug. 22, 1944 P I. $6 2 ii WE a W .:M r PP o as t t flM n e vwWm d 0% e hy Tb Patented Apr. 30, 1946 UNITED SHOCKPBOOF BIEOIBOIIAGNET Theodore H. Spitler, Schenectady, N. 1.,

to Gcneralmectrl New York c Oomparma asslgnor onoi Application August 22. 19, Serial No. 550,523

8 Claims. (Cl. 175-336) My invention relates to electromagnets, more particularly to electromagnets whose armatures are normally in their unattracted positions, and has for it object simple and reliable means for mounting the armature so that it is free from the effects of severe shocks.

My invention is especially applicable to pivoted armatures. A pivoted armature may be ba-L anced about its pivot so as to be substantially free from forces set up by shocks caused by the inerfla oi the armature. However. ordinarily the armature in its unattracted position is brought to rest by a biasing spring against a solid or stationary stop. In the event of a shock. this stop transmits the shock to the armature whereby the armature is thrown toward its attracted position.

In carrying out my invention in one form, I provide stop means for the armature biasing spring together witha relatively weak spring for holding the armature against this stop means when the armature is in its unattracted position. In a preferred form I provide a spring strip extending lengthwise oi the armature and having one end secured to one end of the armature. The other end of the spring strip is provided with a cros member which projects beyond opposite sides of the armature, and when the armature is in its unattracted position, this cross member rests on two stops on opposite sides of the armature. A biasing spring for biasing the armature to its unattracted position bears on this strip at a point adjacent the cross member so that when the armature is in its unattracted position, the force of the spring is applied largely to the stops. However. ii the armature tends to move still farther in the direction toward its unattracted position in response to a shock, the spring strip bends to provide for this movement.

For a more complete understanding oi my invention. reference should be had to the accom- Denying drawing. Fi l of which is a side elevation view of an overload relay provided with an electromagnet embodying my invention; Fig. 2 is a front elevation view of the device of Fig. I; Fig. 3 is a sectional view taken along the line 33 of Fig. 1 looking in the direction of the arrows, while Fig. 4 is a fragmentary view showing a modified form of my invention.

I have shown my invention in one form as applied to the pivoted armature i of a current responsive overload relay having a current coil 2 which is connected in the circuit, such as a motor circuit or the plate circuit of a radio transmitter, to be protected and a resetting coil 3 provided with an armature l.

Upon the occurrence of a predetermined overloadcun'entinthecoulthearmatureiis moved counterclockwise about its central supporting pivot 5 to an attracted position whereby its lower end engages a latch i for the armatm'e 4, moving the latch clockwise about its Pivot 1 against the force of a biasing spring 8 to release the armature. The armature l is thereupon pulled by its biasing spring 9 downward clockwise about its pivot II to its unattracted position, the coil 3 being deenergized. This movement of the armature l correspondingly moves an arm ll secured to it and carryin a bridging contact It. The arm ll moves clockwise about the pivot l8 and moves the bridging member it toward the right hand to disengage the two stationary contacts l3 and II whereby the magnet 2 is deenergized.

Preferably the switch represented by the bridging member l2 and its stationary contacts I: and II is connected in the circuit so as to control the current passing through coil 2 and the device to be protected. Thus, when the bridging member 12 is moved to its open circuit position, the coil 2 is deenergized and the armature i is moved by its biasing spring to its unattracted position, as shown in the drawing. To provide for continued operation. the device is reset byenergizing momentarily the coil 3 by means of a suitable manually operated switch (not shown) such as a push button switch, whereby the armature l is moved to its attracted position and secured in that position by the latch 6. The parts are then as shown in the drawing. the armature I being normally in its unattracted position and moved .only momentarily to its attracted position upon the occurrence of an overload. After the armature l has been reset, the coil 3 is deenergized.

In accordance with my invention, I provide a. resilient stop means for the armature l for limiting its movement to its unattracted position. This stop means comprises a spring strip l6 extending lengthwise in substantially parallel relation with the armature l and having its upper end ll, as seen in the drawing, rigidly secured to the upper end of the armature as by brazing or welding. This strip extends downward along the armature i on the side of the armature remote from the coil 2 to a point below the pivot 5 where the strip it is provided with a transversely extending portion or cross member i8 (Fig. 2). This cross member is may be formed integrally with the strip. Its length is greater than the width of the armature I so that at each end it extends beyond the corresponding side or edge of the biasing spring seated!!! a depression 22 in the strip l6 ad e sr oi H v 22 ogthe prlng I porting P rts to plied'not only to but are applied with suflicient intensity to coii'2. In a clockwise-direction,

2 armature, as seen clearly in Fig. 2. For increased strength, the lower end or edse or the cross portlon IB is bent at right angles toward the armature providing a flange or This rib (9 at its opposite tionnry stops 20 and 2! on opposite position, as ing held against 4 v 15. One end or the sprin jacent its lower end while the spring is seated on an adjustable ber 23, this oint or [5 with the strip being pirates armature I is thereby biased by the spring ii to its unattractcd position strip I6 is bent or shaped tothe lipper end of the armature I the rib I9 is biased against p the armature by' reason-of the spring force e xertcd by the strlpitselt Thus, when the armathe adjacent side 01 'ture is'in its unattracted posltion'tbe force of h -:gtrip libiases counterclockwise about the pivot ifil e. toward its attracted t with the rib IQJThe rib It, as previously stated. is held against-the by the-relatively strong biasposition, into ensazeme supports and-2| ing spring ii. i

Thus it will be observed that, with the'arma- 'ture as shown in its unattracted position, it is biased by the relativelyweak'spring it against a spring .pressed stop which'is the bias against th s stop being,

the flange'or'rib l9,

however, counterclockwise about the pivot 5, l. e., the direction that the armature moveswhen attracted bythe the armatugg has a limited freedom of movement againstthis counspring force applied by the sprine'stri "'Sl'lOCk In a It. Thusshock or component 01 a direction from'the left hand to the seen'in 1, is applied by the supthe pivot 5 and from the pivot 5 to the armature I. However, since the armature is balanced about the pivot, this shock force does right han as not tend to cause rotation of the armature. Any

rebound of the flange l9 from the supports 20 and 2| from such a shock is transmitted to the armature only through the'sprlng strip'li which absorbs the shock so that no appreciable rotation of the armature is produced.

Shock forces in the from the right opposite direction, 1. e., hand toward the left hand, are apthe pivot 5 and to the armature flange 19 to the armature. While the shock may be transmitted by the spring IE to the flange throw the lower end of the armatureaway from the flange, i. e., cause clockwise rotation of the armature, this rotation is in the direction opposite to that required to trip the latch i, and therefore may be neglected. Actually, vhowever, the spring l5 serves to absorb the transmission of shock to the flange I! so that very little clockwise rotation of the armature l is caused by a severe shock.

In the modified form or my invention'shown in Fig. 4. I provide a supporting rod 24 on which the two helical biasing springs 25 and 28 are mounted. This rod extends loosely through a. hole in the armature and at its right-hand end extends loosely through a hole in the supporting bracket 21. It is provided on its right-hand end with a suitable washer and nut, as shown, forming a flange. The spring 25 bears at its right end insuchamannerthat-= 20 against the stop 28 on the rod 2t.

through the spring I! and the 55 on the bracket 21 and at its left 28 rigidly secured to the rod 24.

hand on a dame The spring 25,

which is relatively weak as compared with the spring 28, has its left end seated against a flange 5 29 on the left-hand end of the rod, and its right end bearing against mature 30, thereby to ,17 against the ilange 28, {,1 It will be "understood 10 other parts shown in Fig. 'the springs l5 and I6 and associated with the armature With the armature 16 .as in Fla the adjacent side of the at hold the armature resilientarmature i.

30 in its unattracted position the spring 25 holds the rod 24 in itsleithand extreme position, as shown, while a the weaker 25 countercl thereby holds the lower end observed "that the iorce of the by th s rin -26.

With the arrangement biases the armature in a direction about its pivot and 0! the armature It will be 4 spring 25 is applied in a. direction dpposite to theiorce applied 4; when the coil '25 is energized; the armature is'movedcounterclockwise against the force of the spring 26, the rod 24 sliding toward loose hole ior'it in the served that a shock from the right hand through the bracket 21. It will be ohthe left hand toward 30 the right hand applledto the support is transmltted through the rod the armature, but the 2| and the spring force 0! the shock thus 2Ito transmitted is absorbed to a "very great extent by the spring 25 so that the shock 35 any appreciable counterclockwise armature.

does not produce rotation of the It will be understood that, in the modified term of Fig- 4.4 1s s r gs spring '15 of Fig's'. 1-4! inclusive. 40 definite stop spring IE or 25 in a direction 26 corresponds with the In both forms, a

means is provided for this stron spring while the armature is biased by a weaker toward its attracted position against this stop means. ThusQln Figs.

1-3 inclusive. the spring 15 is means comprising the flange [9 20 and 2|, while the armature spring I6 against the flange l9.

pr vided with'stop and the supports is biased by ,-.t he

While I have shown a. particular embodiment of my invention, it will that! do not wish he understood, oi course, to be limited thereto since many modifications maybe made, and I therefore contemplate any such modifications as spirit and scope of my invention by the appended claims to cover fall within the true What I claim as new and desire to secure by Letters Patent of the United States is:

l. A shockproof electromagnet comprising a support, a coil on said support, otally mounted on 60 tween attracted tively strong an armature pivsaid support for movement beand unattracted positions, a relafirst spring on said support for biasing said armature to said unattracted position, stop means for said first spring for limiting the movement of said armature by and a relatively weak second when said armature is in said tion to apply a force tion opposite to the said first spring, spring arranged unattracted posito said armature in a direciorce applied by said first spring, said second spring yielding to prevent the transmission ol a shock from said support to said armature in a direction to turn said armature on its pivot toward said attracted position.

2. A shockproof support, a coil on said support, 16 otally mounted on said support electromagnet comprising a an armature pivior movement between attracted and unattraoted positions, a relatively strong first spring on said support for biasing said armature to said unattracted position, stop means on said support for said first spring for limiting the movement of said armature by said first spring, a relatively weak second spring'cooperating with said support arranged when said armature is in said unattracted position to apply a force to said armature tending to move said armature toward its attracted position thereby to hold said armatureagainst said stop means, said second spring yielding to prevent the transmission or a shock from said support to said armature in a direction to turn said armature on its pivot toward said attracted position.

3. A shockproof electromagnet comprising support, a coil on said support, an armature pivotally mounted on said support for movement between attracted and unattracted positions, a relatively strong first spring on said support for biasing said armature to said unattracted position, stop means for said first spring for limiting the movement oi said armature by said first spring while providing for additional movement of said armature beyond said unattracted position, and a relatively weak spring carried by said armature for biasing said armature toward said attracted position against said stop means when said armature is in its unattracted position.

4. A shockproot electromagnet comprising a supp rt, a coil on said support, an armature pivotaliy mounted on said support for movement between attracted and unattracted positions, a relatively strong first spring, a member movable by said first spring against said armature thereby to bias said armature to its unattracted position, a stop on said support for said member for limiting the movement of said armature by said first spring, and a relatively weak spring for biasing said armature in an attracted direction against said member.

5. A shock proof electromagnet comprising a coil, an armature for said coll pivotally mounted for movement between attracted and unattracted positions, a spring strip having one end secured to one end of said armature and extending lengthwise of said armature, a stop engaged by the other end of said strip when said armature is in its unattracted position, and a spring engaging said strip adjacent said other end or biasing said strip against said stop and said armature in its unattracted position, said armature when moving to its attracted position engaging said end thereby to move said end away from said stop against the force applied by said biasing spring.

6. A shockproof electromagnet comprising a coil, an armature for said coil pivotaily mounted intermediate its ends {or movement oi a first end to an attracted position with relation to said coil, a spring member having one end secured to said first end oi said armature and extending along said armature to the other side of the pivot of said armature, a cross member on said spring strip having its ends projecting beyond opposite sides of said armature, stationary stop members on opposite sides of said armature, and a spring for biasing said armature to an unattracted position bearing on said spring strip at a point between the plvot of said armature and said cross member thereby to bias said armature to an unattracted position with said cross member in engagement with said stops, said armature in moving to its attracted position engaging said cross member and moving said ems member against the force applied by said spring.

7. A shockprooi elet comprising a support. a coil on said support, an armature pivotaliy mounted on said support for movement between attracted and unatiu'acted positions, a

member extending with respect to said armature on one side oi said pivot, a projection secured to said member intermediate its ends, a relatively strong spring on said member bearing on said support and said proiectlon thereby to bias said member to a predetermined position on said support and said armature to said unattracted position, and a relatively weak spring on said memberbearing on said armature thereby to hold said armature against said projection, said armature when moving on its pivot to its attracted position upon tion of said coil moving said member against the force applied by said relatively strong spring.

8. A shockprooi et comprising a support, a coil on said support, an armature pivotally mounted on said support for movement between attracted and unattracted positions, said armature being provided with an aperture on one side or said pivot, a rod extending loosely through said aperture and having one end extending loosely through an aperture in said support, a first flange on said end oi'said rod, a second fiange secured to said rod intermediate its ends, a relatively strong spring surrounding said rod bearing on said support and said second flange thereby tobiassaidrodtoapositionwithsaidfirstfiange in engagement with said support, a third fiange on the other end of said rod, and a relatively weak spring on said rod bearing on said third flange and said armature thereby to hold said armature against said second fiange. said armature when moving on its pivot to its attracted position upon energization of said coil moving said rod against the force applied by said relatively strong spring.

'rmeonons M. SPITIER. 

